Electrical submersible pumps have been used in oil wells to pump well fluids for many years. These pumps are part of an assembly that includes a submersible motor. The pump assembly is typically suspended on tubing, and a power cable from the surface is strapped alongside the tubing. A motor lead is secured to the lower end of the power cable, the motor lead terminating in a connector that plugs into a receptacle of the motor. This connector is typically known as a pothead connector.
The motor is filled with a dielectric lubricant that is sealed from the exterior at the receptacle. The connector has seals that seal the electrical conductors from well fluid. A variety of connectors are known. In one type, the cable portion of the connector has a housing that contains two rigid insulating members separated by a deformable insulating member. Passages extend through the members for sealingly receiving the insulated electrical conductors. Electrical contact members or pins connect to the conductors and protrude past the forward insulating member. The remaining portion of the housing is filled with an epoxy.
The receptacle portion of the connector has a rigid insulating member with passages for receiving insulated conductors from the motor. Electrical contact members, typically sleeves, are located in the passages in the insulating member. When the cable portion of the connector is connected to the receptacle, the electrical contact pins slide into the electrical contact sleeves. If the motor lubricant becomes contaminated, debris from the oil can encroach into the connector and come into contact with the electrical contact members. The debris can cause electrical arcing in this region. A debris seal is generally included for isolating the sleeves (or pin connections) from debris and to provide dielectric strength between the pins and each pin and ground. Temperature increases in the wellbore may thermally expand the debris seal, that in turn can press outward against the connector assembly and increase internal pressure of the assembly.